Semiconductor device with sidewall wiring

ABSTRACT

Cost is reduced and reliability is improved with a BGA (Ball Grid Array) type semiconductor device which has ball-shaped conductive terminals. A first wiring is formed on an insulation film which is formed on a surface of a semiconductor die. A glass substrate is bonded over the surface of the semiconductor die, and a side surface and a back surface of the semiconductor die are covered with an insulation film. A second wiring is connected to a side surface or a back surface of the first wiring and extending over the back surface of the semiconductor die. A conductive terminal such as a bump is formed on the second wiring.

REFERENCE TO RELATED APPLICATION

This application is a division of Ser. No. 10/420,943, filed Apr. 23, 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a BGA (Ball Grid Array) type semiconductor device which has ball-shaped conductive terminals.

2. Description of the Related Art

A CSP (Chip Size Package) receives attention in recent years as a three-dimensional mounting technology as well as a new packaging technology. The CSP is a small package having about the same outside dimensions as those of a semiconductor die.

A BGA type semiconductor device has been known as a kind of CSP. A plurality of ball-shaped conductive terminals made of a metal such as solder is arrayed in a grid pattern on one principal surface of the BGA type semiconductor device and is electrically connected with the semiconductor die mounted on the other side of the package.

When the BGA type semiconductor device is mounted into electronic equipment, the semiconductor die and an external circuit on a printed circuit board are electrically connected by compression bonding of each of the conductive terminals to each of wiring patterns on the printed circuit board.

Such a BGA type semiconductor device has advantages in providing a large number of conductive terminals and in size reduction over other CSP type semiconductor devices such as an SOP (Small Outline Package) and a QFP (Quad Flat Package), which have lead pins protruding from their sides. The BGA type semiconductor device can be used, for example, as an image sensor chip for a digital camera incorporated into a mobile telephone.

FIG. 22A and FIG. 22B show an outline structure of a conventional BGA type semiconductor device. FIG. 22A is an oblique perspective figure of front side of the BGA type semiconductor device. And FIG. 22B is an oblique perspective figure of a back side of the BGA type semiconductor device.

A semiconductor die 104 is sealed between a first glass substrate 102 and a second glass substrate 103 through epoxy resins 105 and 105 in the BGA type semiconductor device. A plurality of ball-shaped terminals 106 is arrayed in a grid pattern on a principal surface of the second glass substrate 103, that is, on the back side of the BGA type semiconductor device 101.

The conductive terminals 106 are connected to the semiconductor die 104 through second wirings 110. The second wirings 110 is connected with aluminum wirings pulled out from inside of the semiconductor die 104, making each of the ball-shaped terminals 106 electrically connected with the semiconductor die 104.

Detailed explanation on a cross-sectional structure of the BGA type semiconductor device 101 will be given referring to FIG. 21. FIG. 21 shows a cross-sectional view of the BGA type semiconductor devices 101 divided along dicing lines into individual dice.

A first wiring 107 is provided on an insulation film 108 on a surface of the semiconductor die 104. The semiconductor die 104 is bonded on the first glass substrate 102 with the resin 105. A back side of the semiconductor die 104 is bonded on the second glass substrate 103 with the resin 105.

One end of the first wiring 107 is connected to the second wiring 110. The second wiring 110 extends from the end of the first wiring 107 to a surface of the second glass substrate 103. And the ball-shaped conductive terminal 106 is formed on the second wiring 110 extending onto the second glass substrate 103.

Next, a manufacturing process of the semiconductor device 101 will be explained in sequence, referring to FIG. 17 through FIG. 21.

A semiconductor wafer having a plurality of semiconductor dice 104 is provided and its surface is covered with an insulation film 108 made of insulating material such as SiO₂, as shown in FIG. 17. Then the first wirings 107 are formed on the insulation film 108 across borders (dicing lines) S along which the plurality of semiconductor dice 104 is to be cut into individual dice. Line S represents borders between the semiconductor dice 104.

After that, the first glass substrate 102 to hold the semiconductor dice 104 is bonded on the surface of the semiconductor dice 104, on which the first wirings 107 are formed, with the transparent epoxy resin 105.

After back grinding the semiconductor dice 104 to reduce thickness of the dice, the back surface of each of the semiconductor dice 104 and the insulation film 108 are etched along the borders S to expose the first wirings 107.

After that, the etched semiconductor dice 104, side surfaces of the insulation film 108 and exposed portions of the first wirings 107 are covered by the epoxy resin 105, and the second glass substrate 103 is bonded on the back surface of each of the semiconductor dice 104 using the epoxy resin 105 as a binder, as shown in FIG. 18.

Next, the second glass substrate 103 is performed a V-shaped notching along each of the borders S, as shown in FIG. 19. The notching is a cutting process using a cutting tool such as a blade. A V-shaped groove formed by the notching in this process reaches the first substrate 102. With this process, the first wiring 107 is separated into two portions, and their side surfaces are exposed.

An aluminum layer is formed to cover the second glass substrate 103 and cut surface formed by the notching, as shown in FIG. 20. The exposed surface of the first wiring 107 and the aluminum layer are thus connected. After that, the aluminum layer is subject to patterning to make a predetermined wiring pattern and form the second wiring 110.

Next, a protection film 111 such as a solder mask is formed on the second wiring 110, as shown in FIG. 21. Then the ball-shaped conductive terminal 106 is formed on the second wiring 110 through an opening in the protection film 111. Dicing along the borders S follows. With this, the conventional BGA type semiconductor device 101 is completed.

However, there are following problems in the above BGA type semiconductor device 101 and its manufacturing process.

First, the manufacturing process is complicated and expensive, since two glass substrates 102, 103 are used in the manufacturing process of the conventional BGA type semiconductor device 101.

Second, the notching, a peculiar process, is required to cut the first wirings 107, because the second glass substrate 103 is bonded on the back surface of each of the semiconductor dice 104. The notching causes abnormalities on the cut surface at the edge of the first wiring 107, such as incorporation of foreign material or contamination.

Third, there is a possibility that the side surface of the first wiring 107 and the second wiring 110 are disconnected when external stress is applied, because a length of contact between the side surface of the first wiring 107 and the second wiring 110 is only 2 μm to 3 μm. In addition, the side surface of the first wiring 107 is rough and poorly adheres to the second wiring 110, because the side surface of the first wiring 107 is a cut surface formed by notching.

This invention is directed to solve the problems addressed above, and offers a BGA type semiconductor device 101 at a reduced cost. This invention also improves the connection between the first wiring 107 and the second wiring 110 and offers a BGA type semiconductor device 101 of high reliability.

SUMMARY OF THE INVENTION

The invention provides a semiconductor device that includes a semiconductor die, a first insulation film disposed on a top surface of the semiconductor die, a first wiring portion disposed on the first insulation film, and a holding substrate disposed over the top surface of the semiconductor die and holding the semiconductor die. The device also includes a second insulation film having a side film and a back film. The side film is disposed on a side surface of the semiconductor die and the back film is disposed on a back surface of the semiconductor die. The device further includes a second wiring portion disposed on the side film and the back film and connected to the first wiring portion, and a conductive terminal formed on the second wiring.

The invention also provides a manufacturing method of a semiconductor device. The method includes providing a semiconductor wafer having a first die and a second die. A top surface of the wafer is covered by a first insulation film. The method also includes forming a first wiring portion on the first insulation film so that the first wiring portion is disposed above the first and second dice, bonding a holding substrate to the wafer so that the holding substrate faces the top surface of the wafer, and etching a back surface of the wafer along a border between the first and second dice to expose a part of the first wiring portion and to expose a side surface and a back surface of the first die and a side surface and a back surface of the second die. The method further includes forming a second insulation film on the exposed side surfaces and top surfaces of the first and second dice, etching the first wiring portion to cut the first wiring portion in two, and forming a second wiring portion on the second insulation film so that the second wiring portion is connected to one of the cut first wiring portions and extends to the back surface of the corresponding die. The method also includes forming a conductive terminal on the second wiring portion, and separating the first and second dice.

The invention further provides a manufacturing method of a semiconductor device. The method includes providing a semiconductor wafer having a first die and a second die. A top surface of the wafer is covered by a first insulation film. The method also includes forming a first top wiring portion and a second top wiring portion on the first insulation film so that the first and second top wiring portions are disposed above the first and second dice, respectively, bonding a holding substrate to the wafer so that the holding substrate faces the top surface of the wafer, and etching a back surface of the wafer along a border between the first and second dice to expose a part of the first top wiring portion and a part of the second top wiring portion and to expose a side surface and a back surface of the first die and a side surface and a back surface of the second die. The method further includes forming a second insulation film on the exposed side surfaces and top surfaces of the first and second dice, forming a first bottom wiring portion on the second insulation film so that the first bottom wiring portion is connected to the first top wiring portion and extends to the back surface of the first die, and forming a second bottom wiring portion on the second insulation film so that the second bottom wiring portion is connected to the second top wiring portion and extends to the back surface of the second die. The method also includes forming a first conductive terminal on the first bottom wiring portion, forming a second conductive terminal on the second bottom wiring portion, and separating the first and second dice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional view showing a semiconductor device according to a first embodiment of this invention, and FIG. 1B is a cross-sectional view showing a semiconductor device according to a second embodiment of this invention.

FIG. 2 is a cross-sectional view showing a semiconductor device according a third embodiment of this invention.

FIG. 3 is a cross-sectional view showing a semiconductor device according a fourth embodiment of this invention.

FIGS. 4, 5, 6, 7A, 7B, 8A and 8B show process steps for manufacturing the semiconductor device of the first embodiment.

FIGS. 9A, 9B and 10 show process steps for manufacturing the semiconductor device of the second embodiment.

FIGS. 11, 12, 13, 14A, 15 and 16 show process steps for manufacturing the semiconductor device of the third embodiment.

FIG. 14B shows a process step for manufacturing the semiconductor device of the fourth embodiment.

FIGS. 17, 18, 19 and 20 show process steps for manufacturing a conventional semiconductor device.

FIG. 21 is a cross-sectional view showing the conventional semiconductor device manufactured by the process steps of FIGS. 17-20.

FIG. 22A and FIG. 22B are oblique perspective views showing the semiconductor device of FIG. 21.

DETAILED DESCRIPTION OF THE INVENTION

Next, embodiments of this invention will be explained referring to the drawings hereinafter.

FIG. 1A is a cross-sectional view showing a BGA type semiconductor device 1 a according to a first embodiment of this invention. FIG. 1A shows two of BGA type semiconductor dice 2 formed on a semiconductor wafer, after dicing along the borders S. Each of the BGA type semiconductor devices 1 a after dicing is identical with each other. Thus, the structure of one BGA type semiconductor device 1 a will be explained hereinafter.

A first wiring 5 a is formed on an insulation film 6 a, which is formed on a surface of the semiconductor die 2. A glass substrate 3 is bonded on the surface of the semiconductor die 2, using a resin 4 as a binder. The insulation film 6 a is formed of, for example, a silicon dioxide (SiO₂) film, a silicon nitride (SiN) film or an organic insulator film such as polyimide.

The semiconductor die 2 is an integrated circuit die such as a CCD image sensor, for example, and the semiconductor dice 2 is formed on the semiconductor wafer by a semiconductor manufacturing process. The glass substrate 3 is made of transparent glass material with a thickness of about 400 μm. The resin 4 is insulative and is made of a thermosetting epoxy resin, for example. The resin 4 is applied on the entire top surface of the semiconductor die 2 as a binder to bond the semiconductor die 2 and the glass substrate 3.

The first wiring 5 a is a metal pad made of aluminum, an aluminum alloy or copper, and is electrically connected with a circuit element in the semiconductor die 2. The first wiring 5 a is also called an extension pad, because it extends to the border S between the semiconductor dice 2.

The insulation film 16 a is an insulation film covering a side surface and a back surface of the semiconductor die 2, and is formed of, for example, a silicon dioxide (SiO₂) film, a silicon nitride (SiN) film or an organic insulator film such as polyimide.

A plurality of cushions 7 made of a cushioning material is formed on predetermined locations on the insulation film 16 a on the back surface of the semiconductor die 2. The cushions 7 are disposed under conductive terminals 8 and absorb a shock when the conductive terminals 8 are formed on Ni—Au plating placed on a second wiring 9 a. The cushions 7 also function to increase height of the conductive terminals 8 to some extent.

The second wiring 9 a is made of aluminum, aluminum alloy or copper, is formed on the surface of the insulation film 16 a and the cushion 7, and is connected to a side surface of the first wiring 5 a.

Length of contacting portion between the side surface of the first wiring 5 a and the second wiring 9 a is about 2 μm to 3 μm. The width of the contacting portion can be made broad, since the first wiring 5 a is formed broad horizontally.

A ball-shaped conductive terminal 8 is formed on Ni—Au plating placed on the second wiring 9 a through an opening in a protection film 10 a which is formed on the second wiring 9 a.

Next, a second embodiment of this invention will be explained referring to FIG. 1B. Difference between this embodiment and the first embodiment is in a structure of the contacting portion between the second wiring and the first wiring. That is, a portion of a back surface of a first wiring 5 b contacts a second wiring 9 b and is electrically connected with it according to this embodiment, while the side surface of the first wiring 5 a contacts the second wiring 9 a and is electrically connected with it according to the first embodiment. Length of the contacting portion between the second wiring 9 b and the portion of the back surface of the first wiring 5 b is about 2 μm to 3 μm.

Insulation films 6 b and 16 b and a protection film 10 b in this embodiment correspond to the insulation films 6 a and 16 a and the protection film 10 a in the first embodiment.

Since no second glass substrate is used in the first and the second embodiments, a semiconductor device with a reduced height is realized at a less cost than the conventional art accordingly.

And the first wiring 5 a and the second wiring 5 b can be separated by an etching process rather than by conventional cutting process using a blade, since the second glass substrate 103 is omitted. As a result, the side surfaces of the first wirings 5 a, 5 b are made smooth and clean to give better electrical and mechanical connection to the corresponding second wiring 9 a, 9 b, even though the length of the contacting portion is only 2 μm to 3 μm.

Next, a third embodiment of this invention will be explained referring to FIG. 2. The same symbols are assigned to the same components in the figure as in FIG. 1, and explanations on them are omitted.

In this embodiment, a contacting portion between a first wiring 5 c and a second wiring 9 c is formed wider compared with the second embodiment described above. Length of the contacting portion is typically 4 μm to 6 μm, or may be longer. That is to say, the first wiring 5 c has a protruding portion 20 c protruding outwardly from the semiconductor die 2 beyond an insulation film 16 c, in order to obtain wider contacting portion between a back surface of the first wiring 5 c and the second wiring 9 c.

The second wiring 9 c extends from the side surface of the semiconductor die 2 to the protruding portion 20 c forming an L-shape, and contacts with the protruding portion 20 c. The length of the contacting portion between the second wiring 9 c and the protruding portion 20 c is preferably longer than the length of the side surface of the first wiring 5 c. Hence, electrical and mechanical connection between the first wiring 5 c and the second wiring 9 c can be further improved. Insulation films 6 c and 16 c and a protection film 10 c in this embodiment correspond to the insulation films 6 a and 16 a and the protection film 10 a in the first embodiment.

Next, a fourth embodiment of this invention will be explained referring to FIG. 3.

The same symbols are assigned to the same components in FIG. 3 as in FIG. 1, and explanations on them are omitted.

In addition to providing a first wiring 5 d with a protruding portion 20 d so that a contacting portion between the first wiring 5 d and a second wiring 9 d is formed wide, providing a side contacting portion (hereafter referred to as SC) where the second wiring 9 d contacts with a side surface of the first wiring 5 d further improves the electrical and mechanical connection between the first wiring 5 d and the second wiring 9 d in this embodiment.

That is, the second wiring 9 d contacts the side surface of the first wiring 5 d in addition to the contacting area formed wide to have 4 μm to 6 μm of the length of the contacting portion between the back surface of the first wiring 5 d and the second wiring 9 d. The second wiring 9 d may contact entire side surface of the first wiring 5 d. The length of the contacting portion between the back surface of the first wiring 5 d and the second wiring 9 d is preferably longer than the length of the side surface of the first wiring 5 d.

In the first and the second embodiments, each of the second wirings 9 a and 9 b may contact either a portion of or entire side surface of each of the first wirings 5 a and 5 b, respectively.

Next, a manufacturing method according to the first embodiment of this invention will be explained referring to FIG. 4 through FIG. 8B.

First, a semiconductor wafer having a plurality of semiconductor dice 2 is provided, as shown in FIG. 4. The semiconductor dice 2 are CCD image sensors dice, for example. Then the first wiring 5 a is formed over the semiconductor die 2 through the insulation film 6 a across the border (dicing line) S.

After that, the glass substrate 3 is bonded on the surface of the insulation film 6 a on the semiconductor die 2, using the transparent epoxy resin 4. The glass substrate 3 functions as a holding substrate for the semiconductor die 2. After back grinding the back surface of the semiconductor die 2 to reduce the thickness of the die, the semiconductor die 2 and the insulation film 6 a are etched from the backside of the semiconductor die along the border S to expose a portion, preferably a central portion, of the back surface of the first wiring 5 a. The back grinding is not a necessarily required process in this embodiment, and may be replaced by, for example, the etching through the thickness of the wafer.

Cost reduction is possible with this manufacturing process, since it does not have a glass substrate on the backside of the semiconductor die 2, which is required with the conventional art. Number of the manufacturing process steps is reduced, and the semiconductor device itself is made thinner.

Then, the insulation film 16 a is formed to cover the etched side surface of the semiconductor die 2 and the exposed portion of the first wiring 5 a, as shown in FIG. 6. The insulation film 16 a is, for example, a silicon dioxide (SiO₂) film or a silicon nitride (SiN) film formed by CVD (Chemical Vapor Deposition), or an organic insulation film such as polyimide. The insulation film 16 a is about 2 μm thick.

Next, a photoresist 11 is coated on a surface of the insulation film 16 a followed by exposure and development processes, and an anisotropic etching is made on the insulation film 16 a using the photoresist 11 as a mask, as shown in FIG. 7A. An opening 12 with a width of d1 centered around the border S is made in the insulation film 16 a to expose the central portion of the first wiring 5 a.

After that, another anisotropic etching is made using the photoresist 11 and the insulation film 16 a as a mask, to sever the first wiring 5 a in two by completely etching the exposed portion of the first wiring 5 a, as shown in FIG. 7B. Side surfaces of the separated first wirings 5 a are thus exposed.

The etching is done twice to etch the insulation film 16 a and the first wiring 5 a in the above explanation. However, the insulation film 16 a and the first wiring 5 a can also be etched continuously using the same etching gas.

After removing the photoresist 11, a plurality of cushions 7 is formed on desired locations on the insulation film 16 a on the backside of the semiconductor die 2. Only one cushion 7 is shown on the semiconductor die 2 in the figure for the sake of simplicity. This cushion 7 is disposed at a location where the conductive terminal 8 is to be formed.

A metal layer is formed to cover entire back surface of the semiconductor die 2 by sputtering aluminum, aluminum alloy or copper, as shown in FIG. 8A.

As shown in FIG. 8B, a photoresist (not shown) is applied on the metal layer, and exposure and development of the photoresist are made. Using the photoresist as a mask, the metal layer is etched to expose the resin 4 and form an opening 13 with a width of d2, which is smaller than the width d1 of the opening 12 (d1>d2). The second wiring 9 a contacts the side surface of the first wiring 5 a, and both of them are connected electrically and mechanically. The second wiring 9 a is formed to be about 2 μm to 3 μm thick. The length of contacting portion between the first wiring 5 a and the second wiring 9 a is about 2 μm to 3 μm as described above. Nickel and gold are plated on the second wiring 9 a.

Then the protection film 10 a, such as a solder mask, is formed on the Ni—Au plating placed on the second wiring 9 a, and solder is applied through the opening in the protection film 10 a by means of screen printing, for example, to form the conductive terminal 8 on the Ni—Au plating placed on the second wiring 9 a, as shown in FIG. 1A. Dicing along the borders S follows. With this, the BGA type semiconductor device 1 a according to the first embodiment of this invention and shown in FIG. 1A is completed.

Next, a manufacturing method according to the second embodiment of this invention will be explained referring to FIG. 9A, FIG. 9B and FIG. 10. Since process steps corresponding to FIG. 4, FIG. 5 and FIG. 6 are common to the first and the second embodiments, process steps after these steps will be explained.

A photoresist 19 is applied on the backside of the semiconductor die 2, followed by exposure and development processes on it, and an opening 20 having a width of d3 is formed, as shown in FIG. 9A.

Using the photoresist 19 as a mask, the first wiring 5 b is etched and severed in two, forming an opening 14 having the width of d3, as shown in FIG. 9B. Then the photoresist 19 is removed. Note that the width d3 of the opening 14 in FIG. 9B is smaller than the width d1 of the opening 12 in FIG. 7A.

After forming the cushion 7 at a predetermined location on the insulation film 16 b, the second wiring 9 b is formed on a surface of the insulation film 16 b, on the part of the back surface and the side surface of the first wiring 5 b, on the exposed surface of the resin 4 and on the cushion 7, as shown in FIG. 10.

Then a photoresist (not shown) is formed, followed by exposure and development processing, and the second wiring 9 b is etched to form an opening having the same width d3 as the opening 14. With this, as shown in FIG. 1B, the part of the back surface of the first wiring 5 b and the second wiring 9 b make the contacting portion of 2 μm to 3 μm in length, and are electrically connected. The second wiring 9 b is formed to be about 2 μm to 3 μm thick. Nickel and gold are plated on the second wiring 9 b.

Then the protection film 10 b is formed on the Ni—Au plating placed on the second wiring 9 b, and solder is applied to the opening formed at a predetermined location in the protection film 10 b by means of screen printing, for example, to form the conductive terminal 8 on the Ni—Au plating placed on the second wiring 9 b. After that, the dicing is performed along the borders S between the semiconductor dice 2. With this, the BGA type semiconductor device 1 b according to the second embodiment of this invention and shown in FIG. 1B is completed.

Since the manufacturing method of the first and the second embodiments described above does not include the notching used in the conventional art, the first wirings 5 a, 5 b do not have rough surface at the end, and can be kept clean. As a result, the adhesion between the first wirings 5 a, 5 b and the second wirings 9 a, 9 b is improved.

In the manufacturing method of the first and the second embodiments, each of the second wirings 9 a and 9 b is formed by first sputtering over the wide area, and then severing it in two by etching. By doing so, the electrical and mechanical connectivity between the first wirings 5 a, 5 b and the second wirings 9 a, 9 b is improved, even though the contacting portion between them has the same length of 2 μm to 3 μm as in the conventional art.

Although the first wirings 5 a, 5 b are connected with the corresponding second wirings 9 a, 9 b after it is severed in two by etching in the manufacturing method of the first and the second embodiments described above, the first wirings 5 a, 5 b and the second wirings 9 a, 9 b can be severed by etching after the first wirings 5 a, 5 b and the second wirings 9 a, 9 b are connected, respectively.

Next, a manufacturing method according to the third embodiment of this invention will be explained referring to FIG. 11 through FIG. 16.

A semiconductor wafer having a plurality of semiconductor dice is provided, and a couple of the first wirings 5 c are formed on the semiconductor dice 2 through the insulation film 6 c across the border S between the semiconductor dice 2 with a clearance d11. The first wirings 5 c are part of a top layer wiring structure of the semiconductor dice 2, for example.

After that, a transparent epoxy resin 4 is applied over the semiconductor dice 2 through the first wirings 5 c and the insulation film 6 c, as shown in FIG. 12. A glass substrate 3 is bonded on the surface of the semiconductor dice 2, using the resin 4 as a binder.

After back grinding the semiconductor dice 2 to reduce the thickness of the dice, the semiconductor dice 2 and the insulation film 6 c are etched from the backside of the semiconductor dice along the border S to expose a portion of the first wirings 5 c and a portion of the resin 4. The back grinding is not a necessarily required process in this embodiment.

Next, the insulation film 16 c is formed by CVD on the back surface of the semiconductor dice 2, an etched side surface of the semiconductor dice 2, a side surface of the insulation film 6 c, the first wirings 5 c and exposed resin 4, as shown in FIG. 13.

Next, a photoresist 12 is applied on a surface of the insulation film 16 c, followed by exposure and development processes, and an anisotropic etching is made on the insulation film 16 c using the photoresist 12 as a mask to form an opening 15 in the insulation film 16 c, as shown in FIG. 14A. Exposed surfaces of the first wirings 5 c in the opening 15 are called protruding portions 20 c. A width d12 of the opening 15 is formed to be wider than the clearance d11 between the first wirings 5 c. The border S is located at about a center of the opening 15.

After removing the photoresist 12, cushions 7 are formed on the insulation film 16 c, as shown in FIG. 15. After that, a metal layer consisting of aluminum, aluminum alloy or copper is formed by sputtering on the surface of the insulation film 16 c, the surface of the cushions 7, the exposed surface of the first wirings 5 c and the exposed surface of the resin 4. A photoresist 18 is applied on the metal layer, followed by exposure and development processes.

The metal layer is etched using the photoresist 18 as a mask to form an opening 17, as shown in FIG. 16. A width d13 of the opening 17 is smaller than the width d12 of the opening 15 shown in FIG. 14A and FIG. 14B, and is equal to the clearance d11. In other words, a side surface at an end of the protruding portion 20 c coincides with a side surface at an end of the second wiring 9 c.

Then after undergoing the same process steps as the manufacturing method according to the first embodiment, the semiconductor device 1 c of this embodiment as shown in FIG. 2 is completed.

In this embodiment, the back surface of the protruding portions 20 c of the first wirings 5 c is exposed by forming the opening 15 having the width d12 which is wider than the clearance d11 between the couple of the first wirings 5 c. And the protruding portion 20 c and the back surface of the second wiring 9 c make a wide contacting area, the length of which is 4 μm to 6 μm, for example. The adhesion would further increase if the contacting area has a length of more than 6 μm.

Next, a manufacturing method according to the fourth embodiment of this invention will be explained referring to FIG. 14B.

In this embodiment, the etching process described in the third embodiment referring to FIG. 14A is further modified.

FIG. 14B is a cross-sectional view showing a step of partially etching the resin between the wirings 5 d. The etching step shown in FIG. 14A continues to etch through the mask 12 the resin 4 between the couple of separated first wirings 5 d. This etching is either wet etching or dry etching, using an etchant which does not etch the first wirings 5 d.

As a result, a portion of or entire side surface of the first wirings 5 d is exposed. After that, by removing the photoresist 12 and applying the same process steps as in the third embodiment, the semiconductor device 1 d in which the second wiring 9 d contacts the back surface and the side surface of the first wirings 5 d as shown in FIG. 3 is completed.

A plate made of a plastic can be used replacing the glass substrate 3 in the first, second, third and fourth embodiments described above. However, the plate needs to be transparent when the semiconductor die 2 is a CCD image sensor.

As another modification, a film, a silicon substrate, a reclaimed silicon substrate, an oxide film or a transparent resin may be used instead of the glass substrate 3. The film material is made of an organic film material, and is bonded on the first wiring 5 a, 5 b, 5 c or 5 d, through the resin. The film has advantage of reduced cost and no fracturing at the dicing over the glass substrate 3. The reclaimed silicon substrate does not need to be a pure silicon substrate, because it is used as a holding substrate. The reclaimed silicon substrate has advantage of reduced cost. The silicon substrate as well as the reclaimed silicon substrate is bonded on the first wiring 5 a, 5 b, 5 c or 5 d, through the resin. The oxide film is formed by low temperature CVD or by plasma CVD on the first wiring 5 a, 5 b, 5 c or 5 d without resin. The transparent resin, for example an insulation film consisting of transparent epoxy material or transparent polyimide material, is formed on the first wiring 5 a, 5 b, 5 c or 5 d to have a thickness of 100 μm or greater, using screen printing. Each of the film, the silicon substrate, the reclaimed silicon substrate, the oxide film and the transparent resin material is formed to have enough thickness enough to function as the holding substrate. An oxide film or a nitride film is formed as a protection film on the first wiring 5 a, 5 b, 5 c or 5 d, in advance.

The BGA type semiconductor device can be obtained at reduced cost according to these embodiments, since only one substrate supports the semiconductor device. Also, a better electric connection between the semiconductor die and the conductive terminal formed on the holding substrate is obtained. 

1. A semiconductor device comprising: a semiconductor die; a first insulation film formed on a front surface of the semiconductor die; a first wiring layer formed on the first insulation film so that part of a bottom surface of the first wiring layer is in contact with the first insulation film; a second insulation film comprising a side film and a back film, the side film being disposed on an outside sidewall of the semiconductor die and the back film being disposed on a back surface of the semiconductor die; a second wiring layer formed on the side film and the back film so that an edge of the second wiring layer is in direct physical contact with another part of the bottom surface of the first wiring layer; a third insulation film formed on the second wiring layer; and a conductive terminal formed on the second wiring layer.
 2. The semiconductor device of claim 1, further comprising a holding member disposed over the front surface of the semiconductor die and holding the semiconductor die.
 3. The semiconductor device of claim 2, wherein the holding member comprises a glass plate, a plastic plate, a film, a silicon substrate, a reclaimed silicon substrate, an oxide film or a transparent resin plate.
 4. The semiconductor device of claim 1, wherein the conductive terminal penetrates the third insulation film.
 5. The semiconductor device of claim 1, wherein the side film and the back film are made of a same material.
 6. The semiconductor device of claim 1, wherein the outside sidewall of the semiconductor die is slanted so that the front surface of the semiconductor die is larger than the back surface of the semiconductor die.
 7. The semiconductor device of claim 1, wherein the semiconductor die comprises a CCD image sensor. 